Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B1/00—Details of electric heating devices
  • H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
  • H05B1/0227—Applications
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D23/00—Control of temperature
  • G05D23/19—Control of temperature characterised by the use of electric means
  • G05D23/1917—Control of temperature characterised by the use of electric means using digital means
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B3/00—Ohmic-resistance heating
  • H05B3/0019—Circuit arrangements
  • H05B3/0023—Circuit arrangements for heating by passing the current directly across the material to be heated
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B1/00—Details of electric heating devices
  • H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
  • H05B1/0227—Applications
  • H05B1/023—Industrial applications
  • H05B1/0236—Industrial applications for vehicles
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
  • H05B2203/019—Heaters using heating elements having a negative temperature coefficient
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
  • H05B2203/02—Heaters using heating elements having a positive temperature coefficient
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
  • H05B2203/022—Heaters specially adapted for heating gaseous material
  • H05B2203/023—Heaters of the type used for electrically heating the air blown in a vehicle compartment by the vehicle heating system

Definitions

• the invention relates to the detection of overheating of an electric heating device for heating a fluid.
• the electric heating device can be configured to heat, for example, an air flow intended to pass through the heating device.
• the invention can be applied to both a high voltage electric heater and a low voltage electric heater.
• the invention applies in particular to a heating and / or ventilation and / or air conditioning installation for a motor vehicle comprising such a heating device.
• a motor vehicle is commonly equipped with such a heating and / or ventilation and / or air conditioning installation which is intended to regulate the aerothermal parameters of an air flow intended to be distributed in the passenger compartment, in particular the temperature of the air flow.
• the installation generally comprises one or more heat treatment devices, including in particular an electric heating device, otherwise called an electric heater, for heating a fluid such as an air flow.
• the electric heater includes electric heating modules.
• the electric heating modules can be arranged so as to be exposed directly to a flow of air passing through the electric heating device.
• the heating modules include resistive elements, for example with a positive temperature coefficient (PTC), such as PTC stones.
• PTC positive temperature coefficient
• the resistive elements can be supplied by an on-board electrical voltage source, namely batteries.
• An electrical connector connected to the voltage source on board the vehicle can be provided to bring the electrical power required to supply the electric heating device, in particular the resistive elements.
• the resistive elements are controlled by an electronic control unit which generally includes an electrical supply circuit.
• the electrical supply circuit is mounted for example on a printed circuit board.
• a high-voltage electric heater it can be a main vehicle heater and can therefore be very powerful.
• the device can reach a limit temperature at at least one point for the proper functioning of the system.
• CTP stones serve as protection against strong overheating, which can generate a fire, for example, thereby ensuring passenger safety.
• certain components close to the electric heating device such as for example plastic parts of the heating and / or ventilation and / or air conditioning installation, may be more sensitive in particular under certain conditions, for example in the case of a temperature high while the shutters of the heating and / or ventilation and / or air conditioning system are closed, voluntarily or due to an undetected mechanical failure.
• an additional sensor such as a thermal probe which can directly measure the temperature of the electric heating device.
• a thermal probe can for example be arranged in contact with the heating modules or at the level of the electronic control unit, in particular of the printed circuit board. Depending on the temperature detected, the electrical power can be cut or limited.
• this additional sensor which directly measures the temperature generates an additional cost, requires additional space on the printed circuit board and adds weight to the electric heating device. Furthermore, the detection of overheating by this means depends on the distance between the sensor and the resistive elements, and generally on the inertia of the system. In addition, this adds a possibility of additional failure in the event of failure, for example of the additional sensor.
• the invention aims to at least partially overcome these drawbacks of the prior art by providing an alternative solution for detecting overheating of the electric heating device.
• the subject of the invention is a method of detecting overheating for an electric heating device comprising a plurality of resistive elements configured to be supplied electrically by a source of electric voltage, in which the electric supply of the resistive elements is controlled using a control signal by pulse width modulation as a function of a power, temperature or resistance or electric current setpoint.
• Said method comprises the following steps:
• the detection threshold value being representative of an overheating of the electric heating device, as a function of the voltage measured supply and / or said setpoint, or a value of at least one parameter for monitoring overheating of the electric heating device,
• the method may further include one or more of the following characteristics, taken separately or in combination.
• said method comprising an additional step for measuring the value of the intensity of the electric current flowing through a predefined number of resistive elements.
• Said at least one parameter for monitoring overheating of the electric heating device can be a function of the intensity of the electric current.
• Said method can comprise an additional step for calculating the value of said at least one parameter when said at least one parameter is different from the intensity of the electric current.
• the method comprises a step for measuring the supply voltage.
• the duty cycle detection threshold value of the piloting signal by pulse width modulation of the predefined number of resistive elements can also be determined as a function of the measured supply voltage.
• the power supply is a function of a power setpoint.
• the power setpoint can itself be a function of a temperature setpoint.
• Said detection threshold value can be defined as a function of the power setpoint or the temperature setpoint.
• the method may include an additional step for calculating the value of said at least one parameter, when said at least one parameter is different from the intensity of the electric current.
• the value of said at least one parameter can be calculated from the intensity of the electric current flowing through the predefined number of resistive elements measured and possibly from the measured supply voltage.
• the value of said at least one parameter is calculated from said recorded duty cycle.
• Said at least one parameter can be chosen from the electrical resistance of the predefined number of resistive elements, the intensity of the electric current flowing through the predefined number of resistive elements, a multiple or a power of the intensity of the electric current flowing through the number predefined resistive elements, and the electrical power of the predefined number of resistive elements.
• the resistive elements are of the type with a positive temperature coefficient. According to another alternative embodiment, the resistive elements are of the type with a negative temperature coefficient.
• the intensity of the electric current measured is the intensity of the instantaneous electric current flowing through the predefined number of resistive elements, when the control signal by pulse width modulation is 100%.
• Said method can include the following steps: checking whether at least one criterion of said device is representative of a cold state of said device, and inhibiting at least the step of detecting overheating when said at least one criterion is representative of a cold state .
• At least two distinct subsets of resistive elements are independently controlled by pulse width modulation V power supply.
• V power supply For each subsystem, it is possible to independently calculate a value of said at least one chosen parameter.
• a threshold value for detecting the duty cycle of the control signal it is possible to independently define a threshold value for detecting the duty cycle of the control signal, depending on the nature and / or the number of resistive elements of the sub-assembly.
• the invention also relates to a control unit for an electric heating device comprising a plurality of resistive elements configured to be electrically supplied by an electric voltage source, the control unit being configured to generate a control signal by modulation of pulse width of the electrical supply of the resistive elements as a function of a setpoint of power, or temperature, or resistance, or intensity of electric current.
• the control unit includes at least one processing means for:
• the detection threshold value being representative of an overheating of the electric heating device, as a function of the voltage of the measured supply and / or of said setpoint, or of a value of at least one parameter for monitoring overheating of the electric heating device, comparing the value of said cyclic ratio read with the detection threshold value, and
• Figure la shows a flowchart of different stages of the detection method according to a first embodiment.
• Figure lb shows a flow diagram of different steps of the detection method according to a second embodiment.
• Figure 2 is a graph schematically showing an example of an evolution of the electric power and the duty cycle of the pilot signal by pulse width modulation in the event of a drop in air flow.
• the invention is in the field of a heating and / or ventilation and / or air conditioning installation intended to equip a motor vehicle to regulate the aerothermal parameters of the air flow distributed in one or more zones of the passenger compartment of the vehicle.
• the invention relates more particularly to an electric heating device, otherwise called an electric radiator, for a motor vehicle, notably equipping such an installation.
• It is an electrical heating device for a fluid. Without limitation, it may be a device for heating an air flow. Thereafter, the description is made with reference to an air flow, but the invention can be applied to another fluid.
• the electric heating device may be an electric heating device or high-voltage radiator.
• high voltage a voltage higher than 90V or 120V.
• it may be a low voltage radiator.
• the electric heating device is capable of transforming the electrical energy taken for example from the vehicle into thermal energy returned to the air passing through the heating and / or ventilation and / or air conditioning installation 1.
• the electric heating device can include a predefined number of heating modules. These heating modules can be arranged so as to be exposed directly to the air flow passing through the electric heating device.
• the heating modules can each include resistive elements of the positive temperature coefficient (PTC) type.
• the resistive elements are for example made in the form of ceramic stones with PTC effect.
• they may be resistive elements of the negative temperature coefficient (NTC) type.
• the electric heating device generally also comprises an electronic control unit for controlling the heating modules.
• a control unit comprises one or more electronic and / or electrical components.
• the control unit includes in particular an electrical supply circuit (not shown) for the resistive elements.
• the power supply circuit is mounted for example on an electrical circuit support such as a printed circuit board known under the acronym PCB in English for "Printed Circuit Board".
• the power supply circuit includes transistors (not shown), each allowing or not authorizing the passage of current in a predefined number of heating modules.
• the resistive elements are intended to be supplied by an electric power source (not shown), such as batteries, coming for example from the vehicle.
• the power supply of the resistive elements is controlled by pulse width modulation known by the acronym MLI or PWM for Pulse Width Modulation in English.
• the control unit is configured to generate a control signal by pulse width modulation of the power supply of the resistive elements. At least two distinct subsets of resistive elements can be controlled independently by pulse width modulation.
• the electrical supply of the resistive elements can be done according to an electrical power setpoint.
• the device is controlled in a closed loop. Alternatively, the electrical supply of the resistive elements can be done by function of a temperature setpoint, or possibly of resistance, or of electric current intensity.
• FIG. 1a or FIG. 1b a method of detecting overheating for such an electric heating device is described, making it possible to detect in real time any overheating of this device.
• a step E0 can be provided for activating or initializing the process.
• the method includes a step E1 'for reading the setpoint.
• this is a power setpoint P_ (sub) system_target. It could also be a temperature setpoint T_ (sub) system_target, or possibly a resistance R_ (sub) system_target, or even an intensity i_ (sub) system_target.
• the prefix "sub” is written in parenthesis to signify that the instruction concerns a subsystem, respectively all the resistive elements.
• the method can also include a step E1 in which the supply voltage U_battery is noted or measured.
• This step E1 can be implemented by a voltage measurement sensor.
• the supply voltage U_battery can be constant.
• the method can include a step E2, in which the value of the intensity i_system_max or i_subsystem_max of the electric current flowing or measuring is measured or measured. This involves recording the current consumption of the heating module (s) of a subassembly for which we want to monitor a setting. For example, the instantaneous current flowing through the resistive elements is measured.
• This step E2 can be implemented by a current measurement sensor.
• the measured current is for example the maximum instantaneous current or at a peak, when the piloting signal by pulse width modulation is at 100%.
• step E3 the cyclic ratio of the control signal by pulse width modulation is noted from the predefined number of resistive elements PWM_system or PWM_subsystem.
• PWM_ (sub) system with “sub” in parentheses denotes the duty cycle of the control signal by pulse width modulation for a subsystem, respectively for all of the resistive elements. .
• the method may include a step E4 (see FIG. 1b), in which the value of at least one parameter is calculated for monitoring overheating of the electric heating device.
• this parameter is a function of the intensity of the electric current flowing through the predefined number of resistive elements i_subsystem_max, or even all of the resistive elements i_system_max, for monitoring overheating of the electric heating device.
• This step E4 can be implemented by a processing means such as a computer. It can be the actual value of the parameter.
• the value of the parameter can be calculated from the intensity of the electric current i_system_max; i_subsystem_max traversing the predefined number of resistive elements measured in step E2.
• the supply voltage U_battery measured in step El, when this step El is implemented, can also be taken into account in the calculation of step E4.
• one or the parameter can be a function of the value recorded from the duty cycle of the control signal by pulse width modulation of the predefined number of resistive elements PWM_ (sub) system.
• This step E4 can be carried out for one or more subsystems, that is to say for one or more sets of heating modules controlled by one or more transistors, or for the whole system, that is to say the set of resistive elements for all heating modules.
• the parameter can be the electrical resistance of the predefined number of resistive elements R_system; R_subsystem, the electric power of the predefined number of resistive elements P_system; P_subsystem, the intensity of the electric current flowing through the predefined number of resistive elements i_system_max; i_subsystem_max, a multiple or power of the intensity of the electric current flowing through the predefined number of resistive elements.
• the calculation step E4 is implemented when the parameter chosen is not the intensity of the electric current.
• the parameter may not be a function of the intensity of the electric current. It can be for example the temperature of the resistive elements.
• a threshold value for the cyclic ratio detection of the piloting signal is defined by pulse width modulation of the predefined number of resistive elements PWM_ (sub) system_lim, the detection threshold value being representative of a electric heater overheating.
• This threshold value for detecting said cycle report PWM_ (sub) system_lim can be defined as a function of the setpoint, preferably the power setpoint P_ (sub) system_target, noted at step El ’, as shown diagrammatically in FIG.
• the detection threshold value PWM_ (sub) system_lim can be defined as a function of the torque of the measured supply voltage U_battery El and of the setpoint, preferably the setpoint of power P_ (sub) system_target, taken in step El '.
• both step El and step El ' are implemented beforehand, as shown diagrammatically by the dotted arrow between El and E5 and the arrow in solid line between El' and E5 in FIG. .
• the threshold value for detecting duty cycle PWM_ (sub) system_lim can be defined as a function of the value of the chosen parameter calculated in step E4, as shown diagrammatically in FIG. of electric current recorded in step E2.
• the detection threshold value can also be defined as a function of the torque of the supply voltage U_battery measured in step E1 and of the value of the chosen parameter which has been calculated in step E4.
• both step E1 and step E4 are implemented beforehand, as shown diagrammatically by the dotted arrow between E1 and E5 and the arrow in solid line between E4 and E5 in FIG. 1b.
• the detection threshold value can also be defined as a function of the torque of the supply voltage U_battery measured in step E1 and of the value of the electric current intensity noted in step E2.
• step E6 the value measured from the duty cycle PWM_ (sub) system in step E3 is compared with the detection threshold value PWM_ (sub) system_lim) defined in step E5 or predetermined.
• This step E6 can be implemented by a processing means such as a comparator. Depending on the comparison result, overheating can be detected. In other words, if the value recorded from the duty cycle reaches or exceeds the defined duty cycle detection threshold value, this corresponds to overheating of the device. The value recorded from the duty cycle may exceed the detection threshold value, by being higher or lower, depending on the nature of this parameter and on the nature of the resistive elements. In this case, one or more actions against this overheating, not detailed below, can be implemented. If not, the process steps can be repeated until overheating is detected in step E6.
• a processing means such as a comparator.
• one or the parameter can be the electrical resistance of the heating modules.
• R_ (sub) system is designated with “sub” in parenthesis, the value of electrical resistance for a subsystem, respectively for all of the resistive elements.
• the duty cycle detection threshold value PWM_ (sub) system_lim is determined in step E5 according to the electrical resistance value of the number predefined resistive elements R_ (sub) system calculated in step E4 and possibly also the supply voltage U_battery measured in step El.
• This determination can be made for one or more subsystems, that is to say for one or more sets of heating modules controlled by one or more transistors, or for the whole system, that is to say the whole. resistive elements for all heating modules.
• one or the parameter can be the electric power of the predefined number of resistive elements.
• This second approach can be implemented as a variant or in addition to the first approach.
• step E4 an electric power value of the predefined number of resistive elements P_system; P_subsystem from the supply voltage (U_battery) and the intensity of the electric current i_system_max; i_subsystem_max measured.
• the duty cycle noted in step E3 is also taken into account for the calculation of the electric power in step E4.
• the electric power can be calculated by making the product of the instantaneous electric current intensity, the supply voltage and the duty cycle.
• the duty cycle detection threshold value PWM_ (sub) system_lim can be determined in step E5 as a function of this electrical power value of the predefined number of resistive elements P_ (sub) system calculated in step E4 and possibly of the supply voltage U_battery measured in step El.
• step E6 the value of the duty cycle PWM_ (sub) system noted in step E3 is compared with the detection threshold value PWM_ (sub) system_lim) thus determined in step E5.
• one or the parameter can be the intensity of the electric current flowing through the predefined number of resistive elements. This third approach can be implemented as a variant or in addition to the first approach and / or the second approach.
• This third approach differs from the second approach in that there is no calculation step E4 but the value of the parameter is measured in step E2.
• the duty cycle detection threshold value PWM_ (sub) system_lim can be determined in step E5 as a function of the value of the intensity i_system_max or i_subsystem_max measured in step E2 and possibly of the supply voltage U_battery measured at step El.
• step E6 the value of the duty cycle PWM_ (sub) system noted in step E3 is compared with the detection threshold value PWM_ (sub) system_lim) thus determined in step E5.
• the parameter can also be a multiple or a power of the intensity of the electric current flowing through the predefined number of resistive elements.
• the value of such a parameter can for example be measured.
• FIG. 2 illustrates different operating phases of the electric heating device comprising a predefined number of heating modules each comprising resistive elements, for example of the positive temperature coefficient (PTC).
• PTC positive temperature coefficient
• the curves of the electrical power P, the duty cycle of the piloting signal PWM_ (sub) system, and the air flow F are shown diagrammatically.
• phase A the device operates without anomaly, under normal conditions of use, in particular with regard to the air flow and the temperature of the air flow.
• Phase B corresponds to a first drop in air flow as represented by curve F, this drop in air flow.
• phase B the duty cycle of the control signal by pulse width modulation PWM_ (sub) system increases to avoid a drop in power, without however reaching the duty cycle detection threshold value PWM_ (sub) system_lim defined at step E5 (also referring to FIG. la or lb).
• PWM_ (sub) system_lim defined at step E5 (also referring to FIG. la or lb).
• this compensation makes it possible to maintain the power during phase B.
• the graph illustrates a second drop in air flow at the end of phase B.
• the duty cycle of the control signal by pulse width modulation PWM_ (sub) System increases further to avoid a drop in power.
• the duty cycle cannot increase beyond the duty cycle detection threshold value PWM_ (sub) system_lim defined in step E5.
• PWM_ (sub) system_lim the duty cycle detection threshold value
• this corresponds to the detection of an overheating of the device in step E6.
• the detected duty cycle value exceeds the defined duty cycle detection threshold value by the top, that is to say by being higher.
• steps E0 to E6 have been indexed, first step, second step, and so on. It is a simple indexing to differentiate and name the different stages of the process. This indexing does not necessarily imply a priority of one step over another. The order of certain steps in this process can be reversed without departing from the scope of this description. This indexing does not imply an order in time either. Certain steps can for example be carried out at the same time.
• the method according to one or other of the variants described above may further comprise at least one verification step, in which it is checked whether a criterion of the electric heating device is representative of a cold state.
• the criterion is for example the temperature of an electrical circuit support on which is mounted an electrical supply circuit of the resistive elements.
• the temperature of the electrical circuit support is taken, for example by a temperature sensor, such as a thermal probe with negative temperature coefficient.
• the measured temperature reaches or exceeds a predefined threshold representative of a minimum heating of the electric heating device, this confirms that the device is ready to be detected.
• the method may include a step to inhibit at least the step of detecting overheating as long as the criterion, such as the support temperature of the electrical circuit, is representative of this cold state.
• the predefined threshold can be a minimum value below which, no attempt is made to detect overheating.
• Such a verification can for example be carried out in step E0.
• the implementation of the overheating detection method as described above can be done by a control unit.
• the overheating detection method can be implemented by the control unit already provided for controlling the heating modules of the electric heating device.
• control unit is therefore configured to monitor overheating according to the detection method described above.
• control unit comprises at least one processing means for implementing the steps of the method described above.
• control unit includes one or more processing means for reading the power setpoint P_ (sub) system_target, or the temperature setpoint T_ (sub) system_target, or the resistance setpoint R_ (sub) system_target, or even the intensity of electric current i_ (sub) system_target.
• the control unit includes for example a voltage measurement sensor for measuring or reading the supply voltage U_battery.
• the control unit comprises for example a current measurement sensor for measuring or reading the current i_ (sub) system_max traversing the predefined number of resistive elements or even all of the resistive elements.
• the control unit comprises for example a processing means for determining or reading the duty cycle of the control signal by pulse width modulation of the predefined number of resistive elements PWM_ (sub) system.
• the control unit may further comprise one or more calculation means, for example for calculating, the value of at least one parameter depending on the intensity of the electric current flowing through the predefined number of resistive elements i_system_max; i_subsystem_max for monitoring an overheating of the electric heating device when this parameter is different from the electric current intensity, in particular from the measurement of the current i_ (sub) system_max and possibly of the supply voltage U_battery.
• one or more calculation means for example for calculating, the value of at least one parameter depending on the intensity of the electric current flowing through the predefined number of resistive elements i_system_max; i_subsystem_max for monitoring an overheating of the electric heating device when this parameter is different from the electric current intensity, in particular from the measurement of the current i_ (sub) system_max and possibly of the supply voltage U_battery.
• the or other calculation means can also be configured to define, a threshold value for detecting the duty cycle ratio of the control signal by pulse width modulation of the predefined number of resistive elements PWM_ (sub) system_lim, the threshold value being representative of an overheating of the electric heating device and being defined as a function of the setpoint or of a value of at least one parameter depending on the intensity of the electric current for monitoring an overheating of the electric heating device possibly previously calculated, or alternatively as a function of the torque of the supply voltage and the setpoint or the value of the parameter.
• the control unit comprises for example at least one comparator for comparing the value recorded from said duty cycle PWM_ (sub) system with the detection threshold value PWM_ (sub) system_lim.
• the control unit can include a calculation means or microprocessor to determine according to the results of the comparisons if there is overheating.
• the microprocessor can evaluate whether the value recorded from said duty cycle is greater than or equal to said threshold value for detecting defined duty cycle.
• the control unit can also include at least one processing means for checking whether a criterion of the electric heating device is representative of a cold state of the device.
• an additional temperature sensor can be provided (not shown in the figures).
• the control unit may include this additional temperature sensor.
• a temperature sensor can be placed on the printed circuit board PCB, for example by being soldered, soldered, or glued. It can be a negative temperature coefficient (NTC) thermal probe whose electrical resistance decreases uniformly with temperature. Alternatively, it could be a positive temperature coefficient (PTC) thermal probe, the electrical resistance of which increases sharply with temperature.
• NTC negative temperature coefficient
• PTC positive temperature coefficient
• the control unit may for example include a comparator for comparing the temperature of the electric circuit support measured with a predefined threshold representative of a minimum heating of the electric heating device. As long as the temperature recorded does not reach this predefined threshold, this is representative of a cold state of said device, and the control unit may include processing means to inhibit the detection of overheating.
• the method according to the invention makes it possible to detect overheating indirectly in real time when the duty cycle reaches a detection threshold value. This will prevent the electric heater from reaching such a high temperature level that even without causing a fire, it may degrade certain surrounding components.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Automation & Control Theory (AREA)
• Air-Conditioning For Vehicles (AREA)
• Control Of Resistance Heating (AREA)
• Safety Devices In Control Systems (AREA)

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• 2018
  • 2018-11-06 FR FR1860226A patent/FR3088121B1/fr active Active
• 2019
  • 2019-11-05 EP EP19818214.9A patent/EP3877772A1/de active Pending
  • 2019-11-05 WO PCT/FR2019/052616 patent/WO2020094969A1/fr unknown
  • 2019-11-05 JP JP2021523714A patent/JP7138789B2/ja active Active
  • 2019-11-05 CN CN201980067824.1A patent/CN112840216A/zh active Pending
  • 2019-11-05 US US17/291,502 patent/US20220004212A1/en active Pending

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